<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script src="https://code.jquery.com/jquery-3.3.1.min.js"></script>
    <style>
        .addinput{
            display: block;
        }
        button:hover{
            cursor: pointer;
        }
    </style>
</head>
<body>
    <div class="container"></div>
    <button id="add">在上方增加输入框</button>
</body>
<script>
    //点击按钮则在上方容器添加输入框
    $('#add').click(function(){
        const addinput = document.createElement('input');
        $(addinput).addClass('addinput');
        $('.container').append(addinput);
    });
</script>
</html>